A control unit (with the aid of a transmitter unit) may transmit data to at least one peripheral unit, which data is received in the peripheral unit (by a receiver unit) and used for operating the actuators or sensors. In this connection, it may also be data in the form of commands which are written into one or more actuators in order to trigger certain actions of a respective actuator, or which are intended to prompt the readout of instantaneous measured values from a sensor. A processing unit may be provided on the part of a respective peripheral unit in order to carry out these processing steps.
For example, the control unit may be a printed circuit board which has a sequencing control (processor) designed for the digital control, and the assigned peripheral units may be implemented as further printed circuit boards which in each case contain sensors (e.g., for measuring current) as well as actuators (e.g., in the form of power electronics, possibly with PWM modulators). The control unit as well as the assigned peripheral unit(s) are connected to each other for the exchange of data (e.g., using an 8b/10b coding) via a serial interface in the form of a duplex interface, for example. It may have a typical bandwidth between 100 Mbit/s and 200 Mbit/s. Such a system is described, for example, in German Published Patent Application No. 10 2004 052 175.
In that case, the data is usually transmitted serially with a specific clock pulse by the control unit to the respective peripheral unit, the latter, by way of timing recovery, being able to generate the clock pulse for the input/output of data and possibly the operation of the processing unit.
For a highly precise control of processes using the regulating device configured in the control unit, it is necessary that the processing unit of the respective peripheral unit, or in general, that the processing of data on the part of the peripheral unit be synchronized in time with the control unit. To that end, it is common to transmit what are referred to as synchronization characters from the control unit to a respective peripheral unit, and specifically, either via an additional synchronization line between the control unit and a respective peripheral unit or during an interruption in the data transmission between the control unit and a respective peripheral unit.